Quote Originally Posted by Skrum View Post
The dilemma is What Is This Ability Actually Giving You.
The answer is nothing if you have given it all away already because someone can cast Disguise Self and has a good Deception modifier. But that's not a problem with the feature.
If the players want to infiltrate an organization via disguise, I'm not going to parse the every minutiae of exactly what they're using.
You're creating a whole new identity. And with the wealth that player characters have, I'm thinking you can do a lot with that, and probably create your own organizations and webs of intrigue. We're talking about insinuating yourself into places and people's lives, not putting on a uniform just so you can walk through a door.
But if one character has disguise self, and one is a changeling or a kenku, and at least one of them had a decent Deception check (and the barb and the ranger can keep their mouths shut to be silent bodyguards), like I'm just going to roll with that. If they have something really applicable, like Silver Tongue, the Actor feat, or just a monster Deception check, I don't see how in practice Infiltration Expertise is really getting you anything additional.
So the feature is equal to a race selection, a spell, a feat, and a different class feature, and it simultaneously doesn't do anything? I can only shrug and say okay.

But again, it sounds like you're achieving an infiltration in the short term, which seems different to me to what Infiltration Expertise can do in the long term.
As the DM, I'm not going to carefully weigh every single possible way this plan could be carried out and decide the exact outcome if they used ability Y instead of X, thus preserving some outcome that only Infiltration Expertise could achieve.
I don't think up until this thread people have really considered what Infiltration Expertise can achieve, and think that it's just the equivalent of a really good disguise check. So if that's how people play it, then I can understand the opinions on it.
Infiltration Expertise is so specific, and skill uses are so NON-specific, whatever it's doing is just gonna get lost in the noise. It's a plot point. It's not a class ability.
You can base an entire campaign around this ability. And skills are non-specific until they aren't. As a DM, you have to adjudicate. If you don't want to, that's fine, but don't project that onto the class feature.